Lubricating oil composition



United States Patent LUBRICATING OIL COMPOSITION lustrated by amyl diphenyl trithioarsenite, phenyl di- (amylphenyl) trithioarsenite and hexyl cyclohexyl phenyl trithioarsenite. 1 In general, the trithioarsenites may be made by react- 5 ing arsenic trichloride with the thiol or thiophenol cor- Allen F. Millikan, Crystal Lake, and Gilford w. Crosby, responding to the l yl or y r p i h h River Forest, 111., assignors to The Pure Oil Company, arsenite which it is desired to make. For example, if it Chicago, 111., acorporation of Ohio is desired to prepare triphenyl trithioarsenite, 49 gms.

(0.45 mol) of thiophenol is dissolved in '200=ml.of abso- No Drawmg' gg if z z fi gg 1956 lute ethanol, 17.9 gms. (0.45 mol) of sodium hydroxide is added, and the mixture is heated to form a sodium 4 Claims. (Cl. 252-464) thiophenate salt. A few milliliters of water are added to the reaction mixture to facilitate solution and reace tion. When the mixture has almost completely gone into This invention relates to lubricating oils, particularly solution, there is added 30.1 gms. (0.165 mol) of arsenic those used in the crankcases of automotive vehicle trichloride, upon the addition of which there is immedimotors, ately formed a white precipitate and a small amount of It is common practice to add to mineral lubricating oils gas. The solid productis filtered and washed with five used to lubricate internal combustion engines various adsuccessive 100-milliliter portions of water to remove byditives for the purpose of imparting to the oil high product sodium chloride. The product is then purified detergency, high load-carrying characteristics, low wear by recrystallization from a benzene-methanol solvent conand low corrosion qualities. Among the well-known taining one part of benzene to three parts by volume of compounds for imparting improved load-carrying and methanol. The yield before recrystallization is approxiwear characteristics are the zinc alkyl thiophosphates and mately 95% of theoretical. After recrystallization the the alkyl, aryl and alkylaryl thiophosphites. yield is approximately 75%. The recrystallized product We have discovered that certain arsensic compounds analyzes 19.7% arsenic and 23.3% sulfur, against theogive to a lubricant better load and wear characteristics retical values of 18.6% and 23.9%, re pectively. 7 than phosphorus compounds. The .arsensic compounds Preparation of trithioarsenites in which R R jand R of our invention, when added to mineral lubricating oil are different may be accomplished by the reaction of in amounts sufficient to give an arsensic content of bearsenic frichlol'ide with miXtllreS 0f sulfhydryl tween 0.1 and 2% by weight of the finished blend, have p unds; r, if pu compounds are desired, alkyl or y an unexpected eifect in improving the load-carrying charchloroarsenites may be prepared as intermediates and acteristics of the lubricating oil. The arsenic compounds converted to the final ester by reaction with the desired of this invention belong to the class represented by the sulfhydryl compound, e.g. general formula Rs Ri -AS Base Rls Base us Bis 40 The triphenyl trithioarsenite prepared as described was in which R R and R are selected from the group added in the amount of 2.1% by weight to a mineral consisting of aryl, alkyl, arylalkyl and alkylaryl radicals lubricating oil composed of 94.1% by weight of neutral and may be the same or different. We prefer those com- Oil having a viscosity of 170 SUS at 100 F., 5.3% by pounds in which R R and R are aryl or alkyl-substi- Weight of basic barium sulfonate and 0.65% by weight tuted aryl groups. As examples of trithioarsenites which 0f s lfurized terpene. The sulfonate was added as a are suitable for the purposes of our invention may be detergent and the sulfurized terpene as a corrosion inmentioned triphenyl, tritolyl, trixylyl, trimethylxenyl, trihibitor in order to approximate a finished motor oil suitethylxenyl, and trinaphthyl trithioarsenites. Where R able for internal combustion engine service. This blend R and R are alkyl groups, it is preferred that they have Was tested for load-carrying and wear-resistant charat least 5 carbon atoms in the chain in order to impart 5 acteristics and compared with similar blends in which a sufiicient solubility of the compound in the oil. As excommercial zinc dialkyl dithiophosphate and triphenyl amples of alkyl and substituted-alkyl trithioarsenites the trithiophosphite were substituted for the triphenyl trithiofollowing may be mentioned: tri-Z-ethylhexyl, triamyl, arsenite. The blends were tested on the 4-Ball, BF. and tri-2-ethylbutyl, tricyclohexyl, tribenzyl, triphenylethyl, Wear machines, which are described by Larsen, Lubricatrilauryl, tristearyl and trioleyl trithioarsenites. tion Engineering, 1, 35-43 (1945). The results of the Trithioarsenites containing different R groups are iltests are given in the following table.

Table Transition Point to High Wear Rate (10 I second Tests) 20 kg., 1 800 Wt. Per- Wt. Per- Wt. Per- Millimoles r.p.m., 5 Min- Antiwear Additive cent Elecent of cent of ofAddittve ute Wear Test mentin Additive Element per 100 gr. Load, kg. Scar Diameter, Additive in Blend inBlend of Blend (constant Temperamm.

starting 0, F., tempera- 50kg. Load tures) None 200 0.88 Commercial zinc dialkyl dithiophosphate, ZH(SP(S)(OR)2)1 7.3(P) 2.6 0.19 6.1 300 0.27 Triphenyltrithioarsenite,AS(SCsH|)s- 19.7(As) 2.1 0.41 5.5 400 0.30 Triphenyl trithiophosphite 8.7(P) 2-0 0.17 5-5 90 0.29

'By examining the foregoing table it will be evident that not only .did the iriphenyl trithioarsenite exceed the triphenyl trithiophosphite and the zinc dialkyl dithiophosphate in the high load-carryig test, but it also was able to carry a load at a much higher temperature without causing excessive wear. In1he5 minute wear test, which is a light-load wear test, there is substantially no difierence between the .trithioarsenite and the .trithiophosphite, although both-were superior to the oil containing neither of time additives The ability of compounds of elements of group VB of the-periodic table to improve the load-carrying ability of lubricating oils cannot be predicted. In a series of tests on similar organoephosphorus, -arsenic, --antimony .mdbismuth compounds in mineral lube oil containing basic barium anlfonaterand sulfurized terpene, the phosphorus, arsenic :and antimony .compounds .all produced low wear rates, hutrth'e bismuthcompound brought about an increase in wear rate. In another series 10f tests in neutral oil blends, the phosphorusor arsenicfcontaining additives :showed low wear rates, but the antimony compound .showed a high wear rate. In the tests reported in the table, although the thiophosphite ester allowed a small increase in temperature for low wear operation with a standard load, :the .trithioarsenite ester brought about a very markedincreasein allowable-operating temperature, namely, from 200 to 400 F.

Although the .test data were determined on a specific trithioarsenite, namely, the triphenyl trithioarsenite, it is to be understood that trithioarsenite esters in general have the ability to unexpectedly improve the load-carryin: characteristics and the wear rate at high temperatures 4 1 of mineral lubricating oils and that this characteristic is particularly marked in the triaryl and alkyl-substituted triaryl esters.

We claim as our invention:

1. A lubricant consisting essentially of mineral lubricating oil and a small amount, sufiicient to enhance the load-carrying and wear-resistant properties of the oil, of at least one compound corresponding to the formula:

In-s

R7SAS R3-S where R R and R may be a radical containing 5 to 18 carbon atoms selected from the group consisting of alkyl, aryl, arylalkyl and .alkylaryl.

2. A lubricant 'in accordance with claim 1 in which the arsenic compound is present in an amount sufficient to produce an arsenic concentration of 0.1 to 2%.

3. A lubricant in accordance with claim 2 in which the compound is a 'triaryl trithioarsenite.

4. A lubricant in accordance with claim 2 in which the compound is triphenyl trithioarsenite.

References Cited in the file of this patent UNITED STATES PATENTS 2,214,444 Varteressian Sept. 10, 1940 2,346,155 Denison Apr. 11, 1944 2,346,156 Farrington Apr. 11, 1944 2,354,536 Nelson July 25, 1944 2,768,192 McLeod Oct. 23, 1956 

1. A LUBRICANT CONSISTING ESSENTIALLY OF MINERAL LUBRICATING OIL AND A SMALL AMOUNT, SUFFICIENT TO ENCHANCE THE LOAD-CARRYING AND WEAR-RESISTANT PROPERTIES OF THE OIL, OF AT LEAST ONE COMPOUND CORRESPONDING TO THE FORMULA: 